Positionable linear friction lock assembly

ABSTRACT

The present invention involves a friction lock device which utilizes one or more friction springs coaxially disposed about a translating rod within an elongated housing. Bias bushings are provided for slidably supporting the rod adjacent one end of each spring. Each bushing defines a sloped shoulder against which the friction spring bears, with the angle of the shoulder calibrated such that the spring is canted to provide a holding force up to a predetermined axial force on the rod, and to permit the rod to slip relative to the spring at greater axial forces without disturbing the integrity of the spring or its coils. The device includes a release or actuation mechanism to partially unwind the springs, thereby reducing the gripping force of the springs and freeing the rod to slide through the springs.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part of U.S. patent application Ser. No. 10/000,596, filed Oct. 24, 2001, which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention concerns positionable linear mechanical locking devices most particularly of the type used for vehicle seating. Specifically, the invention relates to a type of device in which a friction brake is used to restrict axial translation of a positionable rod.

[0004] 2. Description of the Related Art

[0005] Infinitely positionable linear friction lock assemblies are known in the art. This type of lock generally has an elongated cylindrical rod extending through a housing that contains a pair of coiled springs. The rod can be locked with respect to the housing so that axial translation of the rod is prevented. In certain friction locks this is accomplished by a pair of coiled springs wrapped around the rod, each coil spring having a free state inside diameter that is smaller than the outside diameter of the rod. To allow translation of the rod, an actuator is connected to an end of each spring. The actuator partially unwinds both springs, expanding their diameters and thereby reducing the gripping force of the springs on the rod and freeing the rod to slide through the springs.

[0006] A locking device of this type is included in the seat lock of U.S. Pat. No. 6,164,419, issued Dec. 26, 2000, to Tribbett. As shown in FIG. 2 of the Tribbett patent, the positioning rod passes through an actuating release lever. The lock provides adjustable movement of a seat back relative to a seat frame by actuating the lever to release the coil springs from the rod. In such an application, a very large holding force is required in both directions of rod translation. The resulting housing and its multiple springs and bushings generally exceed 88 millimeters in length. Consequently, a long rod is necessary even if the required range of translation is small.

[0007] Additionally, the bushings disclosed by Tribbett include an angled end face for contacting a coil spring end as a load is applied to the rod. In order to maximize the gripping force of the coil spring on the rod, the bushing's faces have a substantially greater acute angle than the natural helical angle of the coil springs, thereby canting the springs and achieving an elliptical cross-section relative to the rod. Tribbett discloses bushing end faces angled 25 degrees to 35 degrees from a line perpendicular to the longitudinal axis of the rod in order to maximize the gripping force of the springs on the rod.

[0008] Another known locking device involves only one coil spring, although the device still requires numerous components, including a pair of carefully machined spring end bushings at each end of the coil spring. Thus, the component count and length of this prior locking device continues to be larger than is desirable for certain applications.

[0009] Locking and adjustment of various positionable members of automotive seating often requires a relatively small package size and a large holding force in only one direction; however, known locking devices do not provide such a friction lock. Additionally, prior known devices do not release the positionable member upon application of a predetermined slip force. Rather, devices generally hold until failure of the springs or other components of the device. Typical known devices fail under loads of 1350 to 1800 kg (3,000 to 4,000 pounds). Additionally, known locking devices for these and other applications fail to provide an inexpensive, simple-to-assemble, and maintenance-free device.

SUMMARY OF THE INVENTION

[0010] An infinitely positionable linear friction lock is disclosed that is calibrated to provide holding up to a predetermined axial slip force and to permit the lock to slip at greater axial force without disturbing the integrity of the lock, thus providing an overload feature that prevents damage to the lock and allows the lock to operate as an energy absorber or safety breakaway device. The lock may still return to its original control functionality when the axial force returns to the design load bearing range. A lock subassembly includes a housing and a bias bushing that slidably supports a translating rod on which one or more friction springs are coaxially disposed.

[0011] The bias bushing defines a sloped shoulder having an angle of incline calibrated to position the spring such that it grips and holds the rod up to the predetermined axial slip force. Coil springs have a natural helical angle that gives the coil spring a slightly elliptical cross-section. As the angle or cant of the spring coils increase relative to a line perpendicular to the axis of the rod, the minor axis of the elliptical spring cross-section decreases relative to the diameter of the rod. Thus, as the angle of incline of the bias bushing is increased, and the coil spring is forced against the inclined shoulder as an axial load is applied to the rod, the coil spring is forced to a cant angle greater than its natural helical angle and the gripping force of the coil spring on the rod increases, therefore providing holding of a greater axial load without slippage of the spring on the rod. Specifically, the lock bias bushing, spring, and rod are structured and arranged to provide the overload feature in the form of the spring sliding on the rod at axial loads greater than the predetermined axial slip force.

[0012] A mounting bracket can be used to mount the lock subassembly so that the lock can provide adjustment and positional locking of a member of a vehicle seat or some other device by disengagement of the mechanical friction brake and translation of the rod. Typical vehicle seating applications include adjustment of headrests, armrests, front and rear seatback incline, seat height, and cushion length.

[0013] The difficulties with prior positionable linear friction locks are overcome in one aspect of the current invention, namely by features of the lock subassembly. The lock subassembly can accomplish sufficient axial load bearing in a first axial direction for the above-noted and other applications with a small number of components and a small size. A first coil spring contained in a housing is coaxially wrapped around the positioning rod. The spring has an inner diameter less than the diameter of the rod, allowing the spring to resist sliding on the rod. The spring is sandwiched between a first bias bushing having a sloped shoulder at one end and a spring release mechanism at its other end. A cap bushing may be located at an end of the release mechanism opposite the spring and mounted in an end of the housing opposite the bias bushing. The cap bushing receives and aligns the release mechanism, retaining it in the housing. Both the bias bushing and the cap bushing include an inner cylindrical surface acting as a bearing surface for the rod.

[0014] Optionally, the lock subassembly may include a second coil spring similarly wrapped around the positioning rod, and sandwiched between the release mechanism, opposite the first spring, and a second bias bushing mounted in an end of the housing opposite the first bias bushing. The second coil spring and bias bushing primarily provides holding in a second axial direction opposite the first direction.

[0015] The housing may be mounted to a vehicle seat and the flange end of the rod attached to an adjustable seat component. The lock prevents movement of the component because the coil springs normally prevent the rod from translating in the housing. The component can be released for adjustment by actuating the release mechanism. Actuation of the release mechanism provides an unwinding torsion on one end of each spring, increasing the diameter of the springs and partially releasing the springs from the rod surface, thus allowing the rod to translate axially through the housing, and thereby releasing the seat component attached to the rod.

[0016] In one embodiment of the invention, the lock includes one bias bushing having an inner bearing surface for receiving the rod therethrough and one coil spring. In one aspect, each bushing defines a counterbore having an obliquely sloped shoulder at the base of the counterbore for receiving and contacting an end of the adjacent coil spring. The shoulder is sloped at a predetermined angle relative to a line perpendicular to the longitudinal axis of the bore in the bias bushing (and therefore, the axis of the rod). The incline of the sloped shoulder is calibrated to accomplish a maximum axial load that can be held by the lock assembly as the rod presses the coil spring against the spring seat. Specifically, an incline can be specified that cants the spring coils only slightly beyond their natural helical angle, thus limiting the decrease in the coil spring minor axis and the contact friction between the spring and rod. The gripping force provided by the angled coil springs is such that the rod slips through the spring at axial loads above a predetermined level without risk of over-stressing and/or plastically deforming the spring coils or causing other types of damage.

[0017] In another embodiment of the invention, the lock includes a bias bushing and coil spring at each end. A different incline and/or coil spring and therefore a different predetermined axial slip force may be used for each bushing, thus providing a different predetermined maximum load in each axial direction, or the inclines and coil spring and therefore the loads may be the same for both axial directions.

[0018] In another aspect of the invention, each coil spring end has a tang formed by bending a short portion of the spring end radially outward. The tang at one spring end extends into a slot defined by the bias bushing, securing the spring relative to the housing. The opposite spring end is engaged by the release mechanism that slightly, rotationally unwinds the spring relative to the housing and rod.

[0019] In another aspect of the invention, two positionable linear friction locks are attached to each side of, for example, a positionable member of a seat, such as a seat back, and also to the seat or seat frame. A single actuator, such as a cable, may be connected to both lock release levers so that the locks may be simultaneously released, thus providing adjustment of the positionable member relative to the seat.

[0020] One object of the invention is to provide an infinitely positionable linear friction lock that features a small length along the axis of the positioning rod, yet provides a large enough load capacity for a variety of applications requiring adjustability to provide a small package size and length for providing particular load capabilities. A further object of the invention is to provide a predetermined axial slip force, thus preventing damage of the lock subassembly.

[0021] One benefit of the invention is that the lock features an override load limit that will allow the rod to translate and provide subsequent functioning of the friction lock. A further benefit is that the lock provides a small package for applications requiring a lower load capacity and small size. Yet another benefit of the invention is that the linear friction lock components may be constructed of a variety of inexpensive materials including steel, aluminum, and plastic depending on the load requirements and mounting characteristics. The linear friction lock is also capable of accommodating a number of different mounting configurations and a number of different release actuator systems.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above mentioned and other features and objects of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0023]FIG. 1 is a perspective view of a positionable linear friction lock according to a first embodiment of the invention;

[0024]FIG. 2 is a partially cut away perspective view of the lock housing subassembly portion of the lock shown in FIG. 1;

[0025]FIG. 3 is a side cross-section view of the lock shown in FIG. 1;

[0026]FIG. 4 is an end view of the lock shown in FIG. 1, shown from the end with the cap bushing and having the cap bushing removed to better illustrate the details of the spring and lever on the interior of the housing;

[0027]FIG. 5 is a perspective view of a positionable linear friction lock according to a second embodiment of the invention;

[0028]FIG. 6 is a side cross-section view of the lock shown in FIG. 5;

[0029]FIG. 7 is a perspective view of an adjustable recline seat assembly having two positionable linear friction locks; and

[0030]FIG. 8 is a perspective view of the lock mechanism subassembly with the lock and control actuation system of the seat assembly of FIG. 7.

[0031] Corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate and explain the present invention. The exemplification set out herein illustrates embodiments of the invention, in several forms, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DESCRIPTION OF THE PRESENT INVENTION

[0032] The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise forms disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings.

[0033] The present invention relates to positionable linear friction lock devices that are particularly suited for use in vehicle seating applications. Although the exemplary embodiments are envisioned for use in adjusting various members of automotive seating, such as front and rear seat backs, armrests, headrests, seat height, and cushion length, the principles of the invention can be employed in a variety of applications in which an infinitely positionable friction lock can be utilized, for example, for non-automotive seating, telescoping stands or similar devices, and door or window extension hardware.

[0034] In general terms, the invention provides for positioning and locking of a rod that extends through a lock subassembly. By mounting one or two of the rod or lock subassemblies to a member of a seat, and attaching the other component to another member of the seat, the two seat members can be positioned and locked relative to each other by the inventive friction lock. By simply releasing the locking means contained within the lock subassembly, the members can be adjusted relative to each other and then re-locked when the lock is re-engaged. The inventive lock also provides an overload feature, allowing lock components to slip relative to each other at loads above a predetermined force without damaging the lock's designed functionality in normal loading ranges. For applications requiring a lower load capacity in a single axial direction, the inventive lock provides a significant reduction in package size: for example the present invention may provide a lock that has a length of as little as 31 mm. With this general background, further details of the invention will be disclosed with specific references to feature numbers and to figures.

[0035] Referring to FIG. 1, a first exemplary embodiment of positionable friction lock 10 includes lock subassembly 50 and positioning rod 30. Lock subassembly 50 includes housing 51, bias bushing 70, coil spring 80, release mechanism 90, and mounting bracket 40. Lock subassembly 50 may also include end cap bushing 60 and cable actuator bracket 100.

[0036] In the first exemplary embodiment, rod 30 includes an elongated cylindrical steel rod having mounting flange 32 at one end. Bracket 40 and flange 32 may be respectively engaged to seat members that are intended to be adjustably relatively positioned. Housing 51 is cylindrical in shape and defines window 55 along the length of the housing through which a portion of release mechanism 90 extends.

[0037] Referring now to FIGS. 2 and 3, bias bushing 70 is mounted to the inside of one end of housing 51. Bias bushing 70 defines an axially located bore 75 sized for slidably receiving positioning rod 30. End 71 of bias bushing 70 also defines counterbored spring seat 72, shown most clearly in FIG. 3. The base of counterbored spring seat 72 forms sloped shoulder 76 that inclines spring seat 72 from a shallow end at bushing top 74 to a deep end at bushing bottom 73. Shoulder 76 is sloped at a predetermined angle of incline 78 relative to line 89, which is perpendicular to the longitudinal axis 79 of bore 75.

[0038] Spring seat 72 is sized to receive first end 81 of coil spring 80. Coil spring body 83 is positioned around and coaxial with positioning rod 30. Spring 80 has a normal or free-state inside diameter that is smaller than the outside diameter of rod 30. With the relative diameters sized in this way, each coil of spring 80 normally grips rod 30 and resists translation of rod 30 relative to spring 80.

[0039] When an axial load is applied on rod 30 in first direction A, first end 81 of spring 80 is compressed against sloped shoulder 76 of bias bushing 70. Sloped shoulder 76 asymmetrically compresses spring 80 against rod 30 creating an increased gripping force of spring 80 upon rod 30. The gripping force of spring 80 on rod 30 and first spring end 81 compressing against bias bushing 70 will further inhibit translation of rod 30 relative to lock subassembly 50.

[0040] More specifically, coil spring 80 has a slight natural helical angle relative to line 89, which is perpendicular to longitudinal axis 79 of rod 30. The angular cant of spring 80 causes spring coils 83 to have an elliptical cross-section along line 89 and thus relative to a perpendicular cross-section of circular rod 30. Therefore, as the angular cant of spring 80 relative to line 89 increases, to the minor axis of spring 80 along line 89 is reduced against the diameter of rod 30. Thus, the gripping force and contact friction of spring 80 on rod 30 increases. For this reason, as first spring end 81 is pressed against sloped shoulder 76 of bias bushing 70 upon rod 30 being loaded in axial direction A, spring coils 83 are further canted by sloped shoulder 76 to incline angle 78, thus increasing the gripping force of coil spring 80 on rod 30.

[0041] Prior art devices provided an incline angle 78 of 25 degrees to 35 degrees in order to maximize the gripping force of spring 80 on rod 30. However, although such devices were capable of withstanding loads of up to 1350 to 1800 kg (3,000 to 4,000 pounds), when the devices were subject to higher loads, device components such as the coil spring were permanently deformed or otherwise damaged. Thus, after being subjected to high loads, the device would no longer function as designed.

[0042] In contrast, inventive friction lock 10 may include an overload feature—a predetermined axial slip force calibrated in part by angle of incline 78 of shoulder 76. Angle 78 can be selected to be high enough relative to first spring end 81 so that lock subassembly 50 will inhibit translation of rod 30 upon application of an axial load on rod 30 in first direction A up to the predetermined axial slip force. However, the same selected incline angle 78 of sloped shoulder 76 will limit the asymmetrical compression of first spring end 81 by sloped shoulder 76, so that rod 30 will slip through spring body 83 upon application of an axial force on the rod in first direction A that exceeds the predetermined axial slip force. Moreover, the predetermined angle 78 limits the cant of spring coils 83 such that rod 30 will overcome the contact frictional holding force of spring coils 83 while maintaining the integrity of the lock. components, i.e., without dislodging, deforming, or otherwise damaging spring 80, and without allowing successive coils to overlap, thereby destroying lock subassembly 50.

[0043] The angle of incline 78 of sloped shoulder 76 ranges between 10 degrees and 25 degrees from line 89, which is perpendicular to axis 79 of bias bushing bore 75. However, the angle of incline 78 of sloped shoulder 76 in the first exemplary embodiment is slightly less than 25 degrees from line 89. By selecting angle incline 78 to be slightly less than 25 degrees, the inventive override feature may be achieved. Although a peak load capacity of at least 400 kg (900 pounds) may be achieved in the specific illustrated embodiment, when the predetermined axial slip force for incline angle 78 is exceeded. Specifically, above 400 to 450 kg (900 to 1,000 pounds) for slightly less than a 25 degree angle of incline 78, rod 30 will slip through spring 80 and lock subassembly 50 without damage to lock subassembly 50 components and without disrupting the integrity of spring 80 or spring coils 83. Friction lock 10 will therefore continue to function normally upon application of subsequent axial forces.

[0044] In addition to varying angle of incline 78 to achieve a specific predetermined axial slip force for friction lock 10, the load capacity and predetermined axial slip force are also determined by other parameters. Specifically, the length, number of coils, diameter, wire size, hardness, and other spring properties and the diameter, hardness, and surface features of rod 30 may also be taken into account and varied in order to achieve a specific load capacity and a specific predetermined axial slip force for absorbing energy or providing a breakaway device.

[0045] For example, in the first exemplary embodiment, friction lock 10, especially well suited for applications such as rear seatback, armrest, and headrest adjustment, includes a predetermined axial slip force in the range of 340 to 450 kg (750 to 1,000 pounds). For this or other applications, the spring and rod parameters are first specified to provide the required load-bearing capacity and then angle of incline 78 is specified to provide the required predetermined axial slip force. Hardened steel rod 30 has a diameter of 10 mm and a surface roughness of 1 micron or 40 micro inches Ra. Coil spring 80 is wound from 1.42 mm hardened steel music wire and includes approximately 8 coils, giving a length of approximately 11.5 mm. Before coil spring 80 is assembled onto rod 30, the inside diameter is 9.55 mm, or slightly less than the diameter of rod 30. The predetermined axial slip force is achieved by selecting an angle of incline 78 of about 25° (degrees).

[0046] A second exemplary embodiment is a bi-directional adjustment device with breakaway limits in the 450 Kg to 585 Kg (1,000 to 1,300 pounds) range. The second embodiment (FIGS. 5-7) depict a bi-directional adjustment device. The specific design parameters for the above mentioned breakaway limits include hardened steel rod 130 having a diameter of 10 mm and a surface roughness of 0.64 microns or 25 micro inches Ra. Coil springs 180 are wound from 1.42 mm hardened steel music wire and include approximately 16 coils in each spring, creating a combined length of approximately 46 mm. Before the coil springs are assembled onto the rod, the inside diameter is 9.55 mm, or slightly less than the diameter of the rod. To provide the specific breakaway force, the predetermined axial slip force was modulated by selecting an angle of incline 178 of 10° (degrees).

[0047] In order to achieve different loads for similar or different applications of friction lock 10, one or more of the above-noted parameters are varied to achieve the desired result. Depending on the size and amount of energy to be absorbed or the breakaway force desired, the structure and arrangement of the spring coil and rod may be varied within these design parameters. The present invention allows for the predetermined axial slip force to approach the amount of force which would cause plastic deformation of the spring. At any point within the range of elastic deformation of the spring, the present invention allows the spring to be elastically deformed until the predetermined slip force is reached, at which point the mechanism is disengaged. This arrangement allows resumption of the operation of the lock once the slip force is no longer applied. For example, increasing the number of spring coils will increase the load capacity and the predetermined axial slip force. Increasing the angle of incline 78 will increase the predetermined axial slip force. It is also possible to use more than one spring for each direction to create the appropriate coil size for the desired functionality. Exact design parameters may be achieved by device modeling or by incremental trials to achieve the desired results.

[0048] In the first exemplary embodiment, first spring end 81 is secured from rotating within housing 51. Spring 80 has first tang 84 protruding radially outward from spring body 83 and located at first end 81 of the spring. Bias bushing 70 may include first catch 77 for engaging first spring tang 81. In the first exemplary embodiment, first catch 77 is an axial slot along an inside wall of counterbored spring seat 72 as shown in FIGS. 2 and 3. Axial slot 77 allows first spring end 81 to translate axially relative to bias bushing 75 as it is asymmetrically compressed at an angle against sloped shoulder 76. However, axial slot 77 prevents first spring end 81 from rotating relative to bias bushing 70.

[0049] Lock subassembly 50 is comprised of at least housing 51, bias bushing 70, and spring 80, and, for embodiments having one coil spring, may be less than 31 millimeters long. Thus, the assembly is suited for applications in vehicle seating that require a small profile and a lower load capacity. Envisioned applications include, but are not limited to, positionable members of automotive seating, for example: armrests, headrests, and lumbar supports.

[0050] In order to easily reposition rod 30 relative to lock subassembly 50, release mechanism 90, shown in FIG. 2, is included in the first exemplary embodiment. Release mechanism 90 applies an unwinding torsion on second end 82 of spring 80. Release mechanism 90 may include C-shaped tube portion 93 connected to lever portion 91. Tube portion 93 receives second spring end 82 and includes first slotted notch 96, or “kick-in,” for contacting second end 82 of spring 80, as best shown in FIG. 3.

[0051] Release mechanism 90 also includes second catch 92 for engaging second tang 85, which protrudes radially outward from spring 80 at second spring end 82. When lever portion 91 of release mechanism 90 is actuated, tube portion 93 rotates about the axis of spring body 83, applying an unwinding torsion to spring 80 via second catch 92. The unwinding torsion displaces second spring tang 85 and thus decreases the resistance of spring 80 to axial translation of rod 30 by increasing the inside diameter of spring body 83 to a diameter that is larger than the outside diameter of rod 30, thereby permitting axial translation of rod 30. The unwinding torsion may also reduce the natural helical angle or cant of spring 80, thereby also increasing the diameter of spring 80 relative to rod 30. In the first exemplary embodiment, first and second spring tangs 84, 85 are located 180 degrees circumferentially apart.

[0052] In addition to first slotted notch 96 protruding across an interior segment of tube portion 93 of release mechanism 90, tube portion 93 can also define slots 97 (FIG. 2) extending along a segment of the circumference of the tube portion. Second catch 92 may be a slotted notch punched into release mechanism 90 at the junction of tube portion 93 and lever portion 91. Lever portion 91 of release mechanism 90 may protrude from the interior of housing 51 through housing window 55 (FIG. 1). The width of housing window 55 along a portion of the circumference of housing 51 must be wide enough to provide sufficient travel of lever portion 91 so that second spring tang 85 is displaced enough and spring body 83 therefore opened enough to allow rod 30 to slip through spring body 83.

[0053] The first exemplary embodiment also includes end cap bushing 60 as depicted in FIGS. 2 and 3. Cap bushing 60 is attached to an interior end of housing 51 opposite bias bushing 70. Cap bushing 60 defines an axially located bore 65 that is sized to receive rod 30. At exterior end 61 of cap bushing 60, bore 65 may include chamfer 62.

[0054] In addition to supporting rod 30, end cap bushing 60 provides for alignment of tube portion 93 of release mechanism 90 within lock housing 51. The end of cap bushing 60 opposite exterior end 61 includes lip 64 on the interior of bushing 60 and shoulder 63 defined by the exterior of bushing 60. Lip 64 and shoulder 63 are sized to couple with tube portion 93. Tube portion 93 rotates around the outside of lip 64, thereby centering the tube portion within and away from the interior of housing 51. End cap bushing 60 also serves to sandwich tube portion 93 between end cap bushing 60 and spring 80.

[0055] Another feature of friction lock 10 is that lock subassembly 50 may include mounting bracket 40, as depicted in FIGS. 2 and 4. Mounting bracket 40 includes flat bracket body 43 having tab holes 46 for receiving tabs 52 extending from housing 51. Tabs 52 pass through tab holes 46 and are crimped around bracket body 43, fastening bracket 40 to housing 51. Extending from bracket body 43 are first and second ear 41 and 42 having mounting holes 45 for mounting lock subassembly 50 to a member of seat 15, for example, seat frame 17 in the exemplary embodiments. Alternatively, mounting bracket 40 may be attached to housing 51 by other fasteners, for example, welding. Other methods known in the art of mounting lock subassembly 50 to seat 15 are also contemplated by the present embodiment of the invention, for example, welding, a coupling boss, a threaded rod or bore, and in-line or offset brackets.

[0056] Positioning rod 30 may include flange end 33 having mounting flange 32 with flange hole 34 defined therethrough and neck portion 31 at the junction of mounting flange 32 and rod 30. Mounting flange 32 is for connecting positioning rod 30 to a member of seat 15, for example, pivot 19 (FIG. 7) in the exemplary embodiments. Rod end 35 opposite flange end 33 may include radius or chamfer 36, removing the sharp outer circumference of rod end 35.

[0057] Referring to FIGS. 1 and 2, to actuate lever portion 91, the exemplary embodiment includes cable actuator bracket 100 for connecting cable actuator 12 (FIG. 8) to lock subassembly 50. As shown in FIG. 4, cable actuator bracket 100 includes loop portion 106 for attaching bracket 100 to housing 51 and back portion 108 forming first and second notch 103 and 104 (FIG. 3), first and second post 101 and 102, and tie 105 for terminating cable 12 or 13 (FIG. 8). Bracket 100 back portion 108 is strengthened by bracket side walls 107. Lever portion 91 also includes cable slot 95 and hook 94 formed by a bent portion of lever portion 91, both for connecting actuating cable 13. Actuating cable 13 will, therefore, rotate release mechanism 90 relative to housing 51, unwinding coil spring 80, and freeing rod 30 to translate through lock subassembly 50.

[0058] Referring to FIGS. 5 and 6, a second exemplary embodiment of positionable friction lock 110 includes lock subassembly 150 and positioning rod 130. The primary difference between the second exemplary embodiment and the first can be understood by comparing FIGS. 3 and 6. While the first embodiment shown in FIG. 3 includes a single bias bushing 70 having sloped shoulder 76 interacting with a single coil spring 80, the second exemplary embodiment shown in FIG. 6 includes first and second bias bushing 170, 160 each having sloped shoulder 176, 166 interacting with first and second coil spring 180, 120, respectively. Therefore, the second exemplary embodiment may provide a predetermined axial slip force in both axial directions A and B that rod 130 translates through housing 151.

[0059] Referring to FIG. 5, lock subassembly 150 may also include housing 151, release mechanism 190, mounting bracket 140, and cable actuator bracket 200.

[0060] Referring to FIG. 6, first biased bushing 170 is mounted or attached to the inside of first end 153 of housing 151 and defines counterbored spring seat 172. The base of counterbored spring seat 172 forms sloped shoulder 176 sloped at first predetermined angle 178 relative to line 189 perpendicular to longitudinal axis 179 formed by first and second bias bushings 170, 160.

[0061] Second bias bushing 160 is mounted or attached to the inside of second end 154 of housing 151. Second bias bushing 160 defines axially located bore 165 sized for slidably receiving positioning rod 130, bore 165 being aligned with bore 175 of first bias bushing 170. Second bias bushing 160 also defines counterbored spring seat 162 forming sloped shoulder 166 sloped at second predetermined angle 168 relative to line 169 perpendicular to longitudinal axis 179 formed by first and second bias bushings 170, 160.

[0062] Release mechanism 190 includes tube portion 193 located in housing 151 centrally between first and second bias bushings 170, 160. First coil spring 180 is trapped between and received by first bias bushing 170 and tube portion 193. Likewise, second coil spring 120 is trapped by and received by second bias bushing 160 and tube portion 193. Release mechanism 190 may include additional features as discussed above for release mechanism 90 of the first exemplary embodiment.

[0063] One feature of friction lock 110 is that lock subassembly 150 may include a predetermined axial slip force in one or both directions A and B along longitudinal axis 179 of rod 130, the slip force in direction A calibrated by angle of incline 178 of first sloped shoulder 176 and the slip force in opposite direction B calibrated by angle of incline 168 of second slope shoulder 166. As with the first embodiment, angles 178, 168 can be selected to be high enough relative to the first or second coil spring 180, 120 so that translation of rod 130 is inhibited upon application of an axial load on rod 130 in either direction A or B. However, the same selected incline 178 or 168 of sloped shoulder 176 and 166 will limit the asymmetrical compression on first or second spring 180, 120 by first or second sloped shoulder 176, 166, so that rod 30 will slip through first and second coil spring 180, 120 upon application of an axial force on rod 130 that exceeds the predetermined axial slip force for that direction A or B of movement, rather than rod 30 deforming and damaging springs 180 and 120 upon application of increasing loads.

[0064] In order to reposition rod 130 relative to lock subassembly 150, tube portion 193 of release mechanism 190 applies an unwinding torsion on the end of first and second coil springs 180, 162 received by tube portion 193. Release mechanism 190 includes catch 192, shown in FIG. 5, for engaging spring tangs 185, 165, shown in FIG. 6. When release mechanism 190 is actuated, tube portion 193 rotates about axis 179, applying an unwinding torsion to first and second coil spring 180, 120 via catch 192, displacing spring tangs 185 and 162 and thus decreasing the resistance of springs 180, 120 to axial translation of rod 130, by increasing the inside diameter of springs 180, 120 to a diameter that is larger than the outside diameter of rod 130, thereby permitting axial translation of rod 130.

[0065] The second exemplary embodiment of friction lock assembly 110 may also include mounting bracket 140, as depicted in FIGS. 5 and 6. While bracket 140 is shown having first and second mounting ears 141, 142, other known mechanisms in the art of mounting lock assembly 150 to a member of seat 15, for example, seat frame 17 shown in FIG. 7, are also contemplated by the invention such as welding, a coupling boss, a threaded rod or bore, and in-line or offset brackets. Positioning rod 130 may include flange end 133 for connecting positioning rod 130 to a member of seat 15, for example, a seat back pivot 19.

[0066] Referring to FIG. 8, two positionable mechanical locks 810 (which may be as described for lock 10 or 110) are connected by connection cable 14. Connection cable 14 is connected to release mechanisms 890 (which may be as described for release mechanisms 90 or 190) and secured by cable brackets 800 (which may be as described for cable bracket 100 or 200) such that movement of release mechanisms 890 is synchronized. Connection cable 14 and release mechanisms 890 are actuated by actuator 12, shown in FIG. 8 to be connected by actuator cable 13. Alternatively, actuator 12 may be connected along a portion of connection cable 14 between mechanical locks 810. Actuator 12 includes a mechanism for moving cables 13 and 14 connected to it, for example, FIG. 8 shows a pushbutton actuator and FIG. 7 shows a lever or rotary actuator. However, other actuator-type mechanisms known in the art may be used, such as a twist, slide, toggle, pull, or pinch actuator.

[0067] Referring to FIG. 7, two positionable mechanical locks 710 (which may be as described for mechanical locks 10 or 110) are shown mounted to seat 15. Seat 15 includes seat bottom 16, seat frame 17, and seat back 18 connected to seat bottom 16 by pivots 19. In the exemplary embodiment shown in FIG. 7, mechanical lock 710 is located along each side of seat bottom 16. Specifically, lock subassemblies 750 (which may be as described for lock subassemblies 50 or 150) are connected to seat frame 17, securing them relative to seat bottom 16. Additionally, positioning rod 730 (which may be as described for positioning rod 30 or 130) is mounted to a portion of seat back 18 that provides pivoting adjustment of seat back 18 about pivot 19 and relative to seat bottom 16. Additionally, the exemplary installation includes the actuator connections according to FIG. 8, actuator 12, actuator cable 13, and connection cable 14.

[0068] In order to adjust the recline of seat back 18 relative to seat 16, lever actuator 12 is rotated, moving actuator cable 13 and connection cable 14 so that release mechanisms 790 (which may be as described for release mechanism 90 or 190) of both lock subassemblies 750, allow positioning rods 730 to translate relative to lock subassemblies 750, and therefore allowing seat back 18 to pivot relative to seat bottom 16. Upon release of lever actuator 12, release mechanisms 790 release unwinding tensions on the coil spring(s) within lock assemblies 710, securing positioning rods 730 relative to lock assemblies 750, thus securing seat back 18 to seat bottom 16.

[0069] Although the various components are generally constructed from steel, the invention also contemplates use of other rigid, durable materials such as aluminum, plastic and tubular steel.

[0070] In order to further overcome the problem of numerous components and excessive lock size, release mechanism 90, 190 features provide an easily constructed, compact, and inexpensive method of both disengaging lock 10, 110 and of supporting second end 82 of coil springs 80, 180, 120. These features and other inventive aspects of the invention provide distinct advantages over other linear friction lock devices. For example, sloped shoulder 76, 176, 166 of bias bushing bore 75, 175, 165, respectively, and first slotted notch 96 of tube portion 93, 193 of release mechanism 90, 190 provide spring biasing and a predictable load capacity for a predetermined axial slip force. Applied loads above the predetermined slip force will cause rod 30, 130 to slip through springs 80, 180, 120, protecting friction lock assembly 10, 110 components from damage.

[0071] While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains. 

What is claimed is:
 1. A friction lock comprising: a housing; a first bias bushing engaged to said housing, said first bushing defining a first bore, said bore defining a longitudinal axis, and said first bushing further defining a first spring seat at one end of said first bore, a base of said first spring seat defining a first sloped shoulder; a rod slidably extending through said first bore of said first bushing along said longitudinal axis; and a first coil spring positioned around and coaxial with said rod, said first spring having a first end capable of being asymmetrically compressed by said first sloped shoulder when a first axial force is applied to said rod in a first direction; said first sloped shoulder and said first coil spring being structured and arranged such that said first coil spring exerts a gripping force on said rod sufficient to fix said rod relative to said housing upon said first axial force being less than a first predetermined gripping force, and that said first coil spring does not exert sufficient gripping force to fix said rod relative to said housing upon a second axial force being greater than said first predetermined slip force.
 2. The friction lock of claim 1, wherein: said first coil spring has a first tang at said first end of said first spring, said first tang protruding radially outward from said first spring; and said first bias bushing has a first catch, said first catch engaging said first tang.
 3. The friction lock of claim 1, further comprising a release mechanism defining an opening for engaging a second end of said first spring and having a lever capable of applying an unwinding torsion to said first spring.
 4. The friction lock of claim 3, wherein said release mechanism further comprises a C-shaped tube portion for receiving said second spring end, said tube portion having a first slotted notch protruding across an interior segment of said tube portion and contacting said second spring end, and said lever is attached to said tube portion.
 5. The friction lock of claim 4, further comprising a cap bushing engaged to said housing and having an interior lip at a first end, said lip coupled with said tube portion of said lever, and said tube portion positioned between said second spring end and said cap bushing.
 6. The friction lock of claim 5, wherein said lock measures less than 31 millimeters in length.
 7. The friction lock of claim 1, further comprising: a second bushing engaged to said housing and defining a second bore aligned with said longitudinal axis, said second bushing further defining a second spring seat at one end of said second bore, a base of said second spring seat defining a second sloped shoulder; and a second coil spring positioned axially between said first coil spring and said second bushing, said second spring disposed around and coaxial with said rod, said second spring having a first end capable of being asymmetrically compressed by said second sloped shoulder when a second axial force is applied to said rod in a second direction.
 8. The friction lock of claim 7, wherein said second sloped shoulder and said second coil spring being structured and arranged such that said second coil spring exerts a gripping force on said rod sufficient to fix said rod relative to said housing upon said second axial force being less than a second predetermined gripping force, and that said second coil spring does not exert sufficient gripping force to fix said rod relative to said housing upon a second axial force being greater than said second predetermined slip force.
 9. The friction lock of claim 8, wherein: said first and second coil springs each have a first tang at said first end of said spring, said tangs protruding radially outward from said first and second springs; and said first and second bias bushings each have a catch, said catch engaging said first tang.
 10. The friction lock of claim 8, further comprising a release mechanism defining an opening for engaging a second end of each said first and second springs and having a lever capable of applying an unwinding torsion to said first and second springs.
 11. A friction lock having a predetermined axial slip force, the lock comprising: a housing; a first and second bias bushing engaged to opposite ends of said housing, each said bushing defining an axial bore and a counterbored spring seat at one end of said bore, a base of said spring seat defining a sloped shoulder, said first and second bushings oriented symmetrically so that said sloped shoulders face each other and said bores define a longitudinal axis; a rod located through said bores of said bushing, said rod defining a flange end; and a first and second coil spring positioned between said first and second bushings and around and coaxial with said rod, each said spring having a first end capable of being asymmetrically compressed by said respective first or second bushing when an axial force is applied to said rod in a respective first or second direction; said first sloped shoulder and said first coil spring being structured and arranged such that said first coil spring exerts a gripping force on said rod sufficient to fix said rod relative to said housing upon said first axial force being less than a first predetermined gripping force, and that said first coil spring does not exert sufficient gripping force to fix said rod relative to said housing upon a second axial force being greater than said first predetermined slip force.
 12. The friction lock assembly of claim 11, wherein said second sloped shoulder and said second coil spring being structured and arranged such that said second coil spring exerts a gripping force on said rod sufficient to fix said rod relative to said housing upon said second axial force being less than a second predetermined gripping force, and that said second coil spring does not exert sufficient gripping force to fix said rod relative to said housing upon a second axial force being greater than said second predetermined slip force.
 13. The friction lock of claim 11, further comprising: a release mechanism defining a tube portion for receiving said second ends of said first and second springs, said tube portion have a second catch for contacting and rotationally displacing said second ends, said release mechanism also having a lever portion for actuating said tube portion and protruding from an interior of said housing.
 14. A friction lock system for adjusting a first seat member relative to a second seat member, comprising at least one friction lock, said friction lock comprising: a housing attached to the first seat member; a first bias bushing attached at one interior end of said housing, said bushing defining a first bore and defining a first counterbored spring seat at one end of said bore, a base of said first spring seat defining a first sloped shoulder; a rod located through said first bias bushing bore and attached to the second seat member; and a first coil spring positioned around and coaxial with said rod, said first spring having a first and second end, said first end capable of being asymmetrically compressed by said first sloped shoulder when a first axial force is applied to said rod in a first direction; said first sloped shoulder and said first coil spring being structured and arranged such that said first coil spring exerts a gripping force on said rod sufficient to fix said rod relative to said housing upon said first axial force being less than a first predetermined gripping force, and that said first coil spring does not exert sufficient gripping force to fix said rod relative to said housing upon a second axial force being greater than said first predetermined slip force.
 15. The friction lock system of claim 14 wherein each said friction lock further comprises: a release mechanism defining a tube portion for receiving said second end of said spring and capable of applying an unwinding torsion to said spring; said release mechanism further defining a lever portion attached to said tube portion, said lever portion capable of actuating said tube portion; and a cap bushing attached at an opposite interior end of said housing, said cap bushing defining a bore therethrough and defining an interior lip at a first end of said bore, said lip coupled with said tube portion of said release mechanism, and said cap bushing positioning said tube portion between said second spring end and said cap bushing.
 16. The friction lock system of claim 15 further comprising: an actuator cable connected to both said lever portions of said release mechanisms such that movement of said levers is synchronized; and an actuator connected to one of said actuator cable and said lever portions such that movement of said actuator moves said actuator cable and both said lever portions; wherein movement of said actuator applies an unwinding torsion to said springs, releasing said rods to translate relative to said housings, thereby allowing movement of said first seat member relative to said second seat member.
 17. The friction lock system of claim 15, each said friction lock further comprising: a second bias bushing attached at an opposite end of said housing, said second bushing defining a second bore therethrough and defining a counterbored spring seat at one end of said bore, a base of said second spring seat defining a second sloped shoulder; and a second coil spring positioned axially between said first and second bushings and around and coaxial with said rod, said second spring having a first end capable of being asymmetrically compressed by said second sloped shoulder when a second axial force is applied to said rod in a second direction.
 18. The friction lock system of claim 17 wherein said asymmetric compression of said second spring grips and fixes said rod relative to said housing up to a second predetermined axial slip force; and said second sloped shoulder determines said second predetermined axial slip force and allows said rod to slip relative to said second spring when said second axial force exceeds said second predetermined axial slip force.
 19. The friction lock system of claim 18 wherein each said friction lock further comprises a release mechanism defining an opening for engaging a second end of each said first and second springs and having a lever capable of applying an unwinding torsion to said springs.
 20. The friction lock system of claim 19 further comprising: a cable connected to one of said lever portions of said release mechanisms such that movement of said levers is synchronized; and an actuator connected to one of said cable and one of said lever portions such that movement of said actuator moves said cable and said lever portions; wherein movement of said actuator applies an unwinding torsion to said springs, releasing said rods to translate relative to said housings, thereby allowing movement of said first seat member relative to said second seat member. 